This invention relates to apparatus for controlling the opening and closing of high-speed shutter doors by detecting the presence or absence of an object in a space.
Such apparatus are constituted, e.g., by photoelectric barriers, which comprise a light source as a transmitter and a photodetector as a receiver and in which the light beam is a continuous signal that is emitted by the transmitter and reaches the receiver directly or after a deflecting reflection. Such systems comprising a transmitter and a receiver are usually described as photoelectric barriers and are relatively expensive and bulky. A transmitter and a receiver are associated with each line to be watched. Their large bulk is particularly due to the fact that in most photoelectric barriers the light source emits light in the visible spectral range and light which is emitted by extraneous sources also in the visible spectral range may be superposed on the light used in the barrier. For this reason the light source must have a particularly high signal amplitude so that a superposition of light from other light sources will be avoided as far as possible. Particularly in interior rooms, such photoelectric barrier can be more easily implemented because light, e.g., from the sun, will not effect a false response of the photoelectric barrier. Where relatively large areas must be watched, a plurality of photoelectric barriers will be required and in most cases will involve high costs of an order of many thousands of deutschmarks and will require intense maintenance.
Apparatus used outdoors or on external walls preferably comprise a detector which is responsive to ultrasonic energy or operates-like a radar. Such detector will not be affected by disturbing light, as is the case with photoelectric detectors. But such detectors have the disadvantage that only moving object can be detected in the area to be watched. If an extraneous object enters into the area to be watched and said object remains in that area without moving, it will not be possible to detect whether the object which has entered is still within the area to be watched or has left that area.
For instance, in the operation of high-speed folding shutter doors it is important to detect whether a vehicle which has passed through the door opening or a person who has entered that area is still partly or entirely in the range of the pivotal movement of the folding doors after some time. Because this cannot be detected by motion detectors, other detectors must be provided if injury to persons and damage to objects and folding shutter doors by the impact of the folding shutter door on persons or objects in the range of movement of the folding shutter door during its opening and closing movement is to be avoided.
That problem is conventionally solved by the provision of rubber bars on the end edges of the folding shutter doors. Said rubber bars are designed to constitute touch detectors, e.g., because they contain an air chamber which in response to pressure applied to the rubber bar delivers a signal through a suitable connecting hose to a switching diaphragm. But such an arrangement has the great disadvantage that the disturbance-indicating signal will be initiated only when an object has impinged on the rubber bar and that the drive means for the folding door wing will be stopped only after a relatively long delay so that damage and particularly injury to persons cannot reliably be avoided particularly in the control of high-speed doors.
Because that problem cannot be solved even by motion detectors, only photoelectric barriers can be used and owing to the influence of daylight they must have light sources having a particularly high luminous intensity with very high signal amplitudes so that the light sources are expensive. For instance, for a detection also of a stretched-out hand of a person or a drawbar of a vehicle or a fork of a fork lift truck or the like, i.e., a horizontal object which is parallel to the floor plane and may be arranged on any of various levels, it will be necessary to provide a plurality of photoelectric barriers and owing to the overall height of such barriers they must be spaced at least a certain distance apart so that objects extending into the space between the light beams of two photoelectric barriers cannot be detected. If such a plurality of photoelectric barriers are used even though they completely watch the desired area, the resulting systems will cost many thousands of deutschmarks.
For this reason it is an object of the invention to provide apparatus by which a plane and/or a small-depth space, such as an opening in a building, can be watched almost in its entirety and even when an object which is disposed in said plane or opening does not move.
A particularly important advantage afforded by the teaching of the invention resides in that the surface or space to be watched can be watched virtually in its entirety because a plurality of transmitters, which may be relatively small, transmit signals to a single receiver. If the transmitters of said plurality are activated in alternation, e.g., in a cyclic sequence, the location of the disturbance within the opening to be watched can be determined by means of an evaluating circuit which is connected to the receiver. The receiver need not be particularly expensive because it need not distinguish between signals coming from a plurality of transmitters at the same but must check only whether a signal is being received from a given transmitter. In the simplest case that signal is a light signal having a defined length or duration so that it is sufficient for the receiver to check the amplitude and duration of the signal. This means that the signals to be transmitted are generated at a certain clock frequency and will activate the various transmitters in a cyclic sequence and on the receiving side can be checked by the common receiver and evaluated to detect a coincidence or deviation. Different from photoelectric barriers, there is no concentrated beam of light but divergent beams of light are used, which are emitted by a plurality of transmitters and are spread over the area in which the common receiver is located. To avoid any difficulties arising owing to the influence of disturbing light, it is preferred to use a transmitter consisting of an infrared-emitting diode and a receiver consisting of an infrared detector. It will be understood that polarized light sources and polarized light receivers can be used too.
For the surveillance of relatively large areas or spaces it will be necessary to provide a plurality of arrays each of which consists of a plurality of transmitters and one associated receiver. It has been found that triangular configurations are particularly desirable. For instance, a rectangular area may be covered by two mutually opposite arrays, one of which covers one and the other of which covers the other of the triangles which together constitute the rectangular area. For the surveillance of relatively high openings, a plurality of such arrays may be required on both sides of the opening if the space is to be watched on all levels. In that case a particularly great advantage afforded by the invention will reside in that complicated systems will not be required but a large number of, e.g., infrared-emitting diodes may be mounted on a bar on which a receiver belonging to the opposite array is interposed between groups of transmitters.
It will be understood that such bar assemblies can be mounted on stationary as well as on movable objects, such as high-speed folding shutter doors. Owing to the favorable design such bars may also be mounted on jambs or on floor surfaces so that it will be possible to watch not only area but by means of the bars and their surfaces in combination to watch also spaces. This ability may be used particularly with high-speed folding shutter doors for a complete surveillance of the space in which such doors move as they are opened.
The surveillance is so sensitive that even gaseous disturbances entering the space being watched, such as billows of smoke, exhaust gases and the like, may initiate a closing of a high-speed door so that such gases cannot enter the space behind such door.
An illustrative embodiment of the invention will now be described in more detail.